Responsivity eta a function of electric current was measured on HgCdTe IR detectors. According to the known values for resistivity and distances between the contacts the dependance of the responsivity on electric field was also measured. It was stated that the detectors. fabricated on crystals with low resistivity, needed unuusually high currents to attain maximum responsivities. The measurements of spectral responses showed that the detectors had their spectral peaks in 7 - 12 μm range. From the dependance of the spectral maximum on the wavelength it is possible to determine the energy gap of the semiconductor and the composition index x. We investigated the resistivity changes as a function of temperature. These changes may be explained by the temperature changes of concentrations and mobilities of carriers. which were measured by the Hall method. With some detectors another unusual phenomenon was observed, namely that the resistivity and the responsivity as function of temperature reached their maximum at 17o K and at 124 K respectively. As the above phenomenon occurs to lower degree with higher currents, we consider the trap-influence on the charge carriers to be responsible for it.